In general, an air conditioning system for a vehicle includes an air conditioner module for cooling and heating the interior of the vehicle.
Such an air conditioner module is configured to cool the interior of the vehicle by performing heat exchange using an evaporator or by introducing cooling water into a heater so as to heat-exchange the cooling water when a heat-exchanging medium ejected by driving a compressor passes through a condenser, a receiver drier, an expansion valve, and the evaporator and then is again circulated in the compressor.
As the concern for energy efficiency and environmental pollution increases, the development of an electric vehicle that is driven using a fuel cell or electricity as a power source, or a hybrid vehicle that is driven using an engine and an electric battery, as a representative example of a green car that substantially replaces an internal combustion engine vehicle, is being required.
Among green cars, the electric vehicle does not use an additional heater, unlike an air conditioning system for a general vehicle, but uses a gas refrigerant at a high temperature under a high pressure as a heating medium in a heating mode. An air conditioning system applied to the electric vehicle is generally referred to as a heat pump system.
In the heat pump system, in a cooling mode in the summertime, the gas refrigerant at the high temperature under the high pressure that is compressed by the compressor, after being cooled and condensed by an outdoor heat exchanger (outdoor condenser), is introduced into the evaporator via the receiver drier and the expansion valve. A low-temperature and low-pressure refrigerant is evaporated by the evaporator through heat exchange with the outside air introduced into a heating, ventilation, and air conditioning (HVAC) module, and allows the air introduced into the HVAC module to be cooled. Air cooled in a state in which an indoor condenser is closed by an opening/closing door of the HVAC module, is supplied to the interior of the vehicle so that the indoor temperature of the vehicle can be lowered.
FIG. 1 illustrates an example of an operating state of a heat pump system of an electric vehicle according to the related art in a heating mode in the wintertime. The heat pump system includes a compressor 1, an indoor condenser 2, an indoor HVAC module 3, an opening/closing door 4, and a positive temperature coefficient (PTC) heater 5. The heat pump system also includes an evaporator 6, in which a refrigerant evaporates during a cooling mode in a heat pump system, a heat exchanger 7 for collecting heat generated in electronic components (e.g., motor, high voltage inverter, etc.) and transferring it to a refrigerant in a heat pump, and a coolant flow 8 for cooling off electronic components (e.g., motor, high voltage inverter, etc.).
In the heating mode in the wintertime, a high-temperature and high-pressure gas refrigerant that is compressed by the compressor 1, moves to the indoor condenser 2 (not an outdoor condenser) via a valve and is heat-exchanged with the outside air absorbed into the indoor HVAC module 3. The outside air that is heat-exchanged in a state in which the indoor condenser 2 is opened by the opening/closing door 4 of the HVAC module 3, passes through the positive temperature coefficient (PTC) heater 5 and is introduced into the interior of the vehicle so that the indoor temperature of the vehicle is risen.
The high-temperature and high-pressure gas refrigerant that is introduced into the indoor condenser 2, is condensed through heat exchange with the absorbed outside air and is again ejected as a liquid refrigerant.
However, in a change of season and in inside air modes, which are low heating load conditions in the heating mode, when, for example, the temperature is moved from a highest temperature to a cooling temperature in the heating mode (when the opening/closing door 4 is moved to a position indicated by a dotted line of FIG. 1), the air flow of the outside air that passes through the indoor condenser 2, is reduced, and the amount of heat exchange with the high-temperature and high-pressure refrigerant introduced into the indoor condenser 2 is reduced. Thus, the inlet temperature of the indoor condenser 2 rises, and the amount of heat dissipation of the indoor condenser 2 is reduced.
Thus, since the pressure of the refrigerant discharged from the indoor condenser 2 increases, power consumed by the compressor 1 increases, and the whole power consumed for air conditioning increases.